Stand-by fuel control for jet engines



Al1gl7, 1954 J. lsREELI ET AL STAND-BY FUEL CONTROL FOR JET ENGINES Filed Aug. 4. 1948 Suk USS Qumkb wm Nm.

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wm s m Patented Aug.. 1,7, 1954 UNITED STATES MENT OFFICE STAND-BY FUEL CONTROL FOR JET ENGINES .lack llsreeli, New York, and William Frantz, Lynbrook, N. Y., and Duncan Ramsay, Wahroonga,

New South Wales,

Australia, assignors to Simmonds Aerocessories, Inc., corporation of New York Tarrytown, N. Y., a

14 Claims.

This invention relates to improvements in fuel control apparatus for jet engines, and more particularly to stand-hy control arranged to take over the metering of fuel to the jet engine in the event of a failure of the main control for the engine.

Jet engines are provided with a main control for metering fuel in accordance with given parameter selections or schedules for which the control and engine is designed. It is highly desirable to have a stand-by or auxiliary control apparatus which will take over the metering of the fuel in case of failure of the main control or of the pump, or other equipment involved in supplying fuel thereto.

The primary object therefore of the present invention is to provide a stand-by control apparatus which is associated with the fuel delivery line from the main control in such a way that it automatically takes over the fuel metering job upon the failure of the main control system or components.

According to the features of the invention, the improved apparatus comprises a combination of a stand-by fuel control system with a main control system and a pipeline for supplying fuel from a fuel supply and for delivering it to the nozzle gallery of the jet engine. The improved combination also includes a separate fuel supply line for the stand-by control system having a fuel metering mechanism associated therewith and connected into the line from the main control, a fuel return line for returning fuel from the said fuel supply lines to the supply tank or tanks, valve means for controlling the flow of fuel from each fuel supply line to the return line, a check valve in each of the fuel supply lines beyond the control valve, means for normally maintaining the control valve between the stand-by fuel supply line and the return line in open position, means for normally maintaining the valve between the main fuel supply line and the return line in closed position, and means responsive to a predetermined drop in the pressure of the fuel in the main fuel supply line in advance of the cheek valve therein for closing the control valve .between the stand-by fuel supply line and the fuel return line.

The apparatus of the present invention also preferably includes means for shifting at will the control and metering of fuel from the main control system to the stand-by control system and vice versa. The apparatus is also desirably arranged so that where there has been a shift automatically from normal operation to emergency control operation, the reverse shift will also take place if the main control comes back into normal operation. The combined systems are arranged to cooperate in maintaining fuel supply to the nozzle gallery of the jet engine or engines, and the stand-by control system is arranged to automatically supply fuel under metering conditions upon failure of the main control, such failure constituting or resulting in a reduction in pressure in the fuel supply line from the main control to a value below the fuel pressure correspending to maximum critical altitude of the engine or any other predetermined value.

Another feature of the invention comprises a novel mechanism for operating the valves for bypassing fuel from the fuel supply lines to the return line, such mechanism including solenoid operated auxiliary valves of small capacity arranged to utilize fuel pressure for operating the main bypass valves.

The apparatus of the present invention includes other features and advantages which will be described in greater detail hereinafter in connection with an apparatus comprising one illustrative embodiment of the invention as shown in the accompanying drawing comprising a broken diagrammatic sectional View.

Referring to the drawing, the fuel normally supplied to the jet engine or engines is drawn from a supply tank through a supply line I0 and forced by means of an engine driven pump I2 through a line I4 which passes into a main metering control system, for example, of known type, shown diagrammatically at I6. The pump I2 may bean integral portion of control I6. From this main control, the metered fuel under normal operating conditions is conducted through a line I8 having a check valve 2i) into a main supply line 22 which delivers the metered fuel to the nozzle gallery of the jet engine or engines.

The fuel for the stand-by control is not taken from the pump I2, which may fail or be put out of action, but is supplied from the fuel supply tank through a separate line 2e and forced by means of a pump 26, driven by any suitable power means, not shown, through a line 28 and metering mechanism 3i] associated therewith, into a line 32 provided with a check valve 34, into the metered fuel line 22 leading to the nozzle gallery of the jet engine or engines.

'Ille apparatus includes a pipe-line or duct 35 for returning fuel from either the line 26 or the line is to the supply tank, this line being connected into the line I8 by a branch line 38 controlled by a valve 46.

Bypassed fuel from the line 2B is delivered to line 3EV through a branch line l2 controlled by a valve M.

The valves 4l) and 44 are `constructed alike and provided with similar operating equipment. For example, the valve 40 is urged to its seated position, as shown, by a light spring, but is held in that position by the pressure of fuel from the line 1S supplied through a duct 4B opening into the line is and controlled by a small Valve 48 operated by a solenoid 56. The -space in-back-of the valve lli) is vented into the return line 38, and this vent is provided withan orifice 52. The arrangement is such that the pressure Aof .liquid owing through the duct 46 .inibackof :the .valve t@ holds it against its seat while a small amount of liquid continuously flows through the orifice E2. The valve 40 is held on its seat because of the equalized pressure in front and in back of the valve, coupled with the fact that thearea of the back of the valve is greater than the area of the .front of the valve projecting through its seat and facing into the line I8. When the small valve i8 is closed by the solenoid ,50, the pressure in back of the valve it falls off because .Of leakage through orifice 52, so that pressure in the line I8 moves the valve t to open position, to permit the bypassing of fuel through the lines 38 and 3S. The valve hl operates in the same Way and its associated elements are given the same numbers as the valve 40, plus the letter a- When engine fuel is being supplied under control of the main system i8, that is, through the line i8, the valve it is closed and vthe valve 48 open, while the valve 44 is open and the small solenoid operated valve 48a is closed. Thefuel owing through the line lll therefore opens .the check valve 2t and fuel pressure closes the check valve 313.

A differential pressure switch mechanism is associated with the line i8 and responsive to a pressure drop therein for de-energizing the .s olenoid 50u, opening valve 58a and effecting Ythe closing of the valve 44 so that fuel will be supplied through'the .lines 23 and 32 to the engine supply line `22. This .mechanism includes a shuttle like actuator .54 urged to its upper position by a spring ,56 and urged to its lower .position against the spring by the v,pressure of .fuel from the line Ylll supplied through a duct 58, an adjustable pressure relief valve .5E and a duct .62. The actuator Ell is ,provided-with an external camlike surface S4 which engages vand movesa pin 66 when the actuator is pushed down by -the pressure of the fuel. The actuator ..54 is .also drilled asshownandprovided with an orice .G8 through which fuel may ow into the lower portion of the valve cavity and through a duct 70 to a fuel return line such `as 36. When .the pin 3S is moved tothe right by the shuttle like actuator d, it moves a block 'H cna diaphragm seal to in turn move a pin i3 to close the contacts 'i2 of a switch This switch is pivoted in its mounting on a pin l5, at its upper righthand corner, and is adjustable with respect to the block i by a spring '15a and screw 15b as shown. The switch lll may be vpivoted on the pin with or against the action of the spring .laby operating the screw 15b so that the switch Ycontacts 'i2 will be open when .theactuator '54 is .up and will be closed when the actuator 54 is Vpushed down to the desired extent by the fuel pressure.

The adjustable pressure relief valve 60 is mounted in a cavity and is responsive to the pressure in the Yline IB. This valve is adjusted 4- by a screw 'I6 and associated spring to control the pressure at which the stand-by system will be cut in and out. When the pressure in the line I8 is up to normal operating pressure the valve 6D will be in its .upper position so that fuel will now through lines and 62 and force the shuttle like actuator 5f! down, thereby closing the switch contacts 12. The cavity of the adjustable valve G and the cavity to the left of the diaphragm carrying the block 'H are Vented to fuel return by lines 'il so that the valve 6i) moves freely in Aresponse to the pressure in the fuel line i8, and ,pressure is not built up against the diaphragm by leakage around pin t6.

The contacts 'i12-of the switch 'lll are connected by -wires 18 .and 80 to the terminals of a switch 82, .the wire '18 also being connected into an associated source of electric current such as abattery 8G, while the wire 86 is also connected by wires 86 to the solenoid 5Go. The battery 84 and solenoids B and 50a are grounded. It will be seen that as long as the contacts of switch i4 are together, current ows from the battery lfill through-the wire 18, the switch contacts l2, vthe wires Sil and'86 and the solenoid Sila, so that the latter is energized to keep the valve 48a closed and permit the opening-of the valve M. This is the position of theapparatus during normal operation of the system, it being understood -of course that the main control l@ is set by levers 88 connected to the pilots, or the operators control lever 9G.

If for any reason the pump i2 or `the main control I5 should .fail and the pressure of fuel in the line IE fall off to the predetermined set value, the valve 60 would ,close oif the flow of fuel through the line62 and the shuttle like actuator '5d would assume its upper position under action of the spring 56 because of the leakage through the orifice 68. This will cause separation of thecontacts Y"l2 and the deenergizing Yof the solenoid 50a, which would permit the 'flow of fuel'through the duct Sz to equalize the pressure on opposite sides of the vvalve lill, thereby f permitting the spring to move it to closed position, so ythat fuel would then be supplied to the engine from the stand-by control system, including the line 32. As soon as pressure builds up in the lines-32 and 22, the check valve 2l] will automatically be closed.

.Thestand-by control apparatus is arranged so that the pilot or operator .may deliberately select .it at any time .by pressing a switch button 92 which operates a switch 913. As an example, if the pilot oroperatordesires to use the stand-by control in starting vthe engine, he pushes downv on ,the 'button 92 to close theswitoh 9G. It will be noted that at .this time with no fuel pressure iin line i8, .the shuttle like actuator 5G is up. The switchi32 is open and the solenoid 53a is de-energized so that valve li will close as pressure builds up in the line 2S. The closing o the switch 91% sends current from the battery ll through a wire 9S to the solenoid 5L to close the valve e3, whichresults in the opening of the valve it when fuel pressure develops in the line I8 as the engine starts, the pump l2 being an engine-driven pump. After the stand-by control is once selected by operation of the .switch handle 92, it will .continue operation until the switch handle is raised. Once theswitchrhandle is raised, the main control .will come .into operation .inthe manner explained above andoverride the stand-by control.

The main .and stand-'by Acontrols are advantageously correlated so that the stand-bycontrol is designed to meter fuel in sufficient quantity to maintain engine operation and at some fuel pressure value below that selected for the main control. Therefore, as long as the main control operates normally, its pressure overrides the po tential pressure of the stand-by control and actuates the shuttle valve 54 so that the solenoid ta is energized and the valve 44 opened. From the foregoing it will be understood that if the main control should operate erratically, the pilot or operator may put it out of action at any time and elect to control the engine with the standby control by merely closing the switch 94 while maintaining `switch 82 open.

When it is desired to cut off the supply of fuel to the engine, both sclenoids 50 and 50a are energized by pressing the switch button 92 and a switch button 98 which respectively close switches 94 and |32. The valves 40 and 44 are then permitted to open, regardless of which control systern is being used. The springs of the check valves 20 and S4 are rated with respect to the springs of the valves 40 and 44 so that they will close, while the valves 40 and 44 may be pushed open.

The metering system included in the stand-by control apparatus and connected between the fuel supply lines 28 and 32 includes combinations of elements arranged to utilize various orifice sizes and varying fuel pressures. It is to be under stood that iiow through a Xed orce can be controlled by varying the pressure drop across it; or for constant pressure drop, flow may be controlled by varying the area.

The stand-by control in the present instance is arranged to supply fuel to the engine according to a given speed selection schedule and according to the total intake pressure received by the engine. The speed scheduling is obtained by the pilots operation of a rotary speed jet device Uli@ opening into the line 28 and connected to a lever |02 having a linkage |04 connected with the linkage S8 and the pilots control lever 33S. The speed jet device |06 includes an open-top rotatable cylinder I 05 connected to lever |02 and having a variable area orice |06 which delivers fuel through a duct |67 of oblong cross-section opening through a cylinder surrounding the cylinder |05 and arranged to take the flow through whatever area of the orifice coincides with the inlet of the duct |07. When the pilot rotates the cylinder |05 of speed jet |00 he selects a particular area for the flow of fuel, this area representing the desired speed selection.

The fuel delivered through the duct or passageway |07 owsthrough ports |23 in a regulator valve body 0 and then into line 32 containing the check valve 34.

The regulator valve body ||0 carries a closure member |2 urged away from its seat by a spring i4 and urged to its seat by the pressures acting across a diaphragm i 6 attached to a valve shaft IIB.

Metering pressure across the speed jet itil is regulated by movement of the valve closure memM ber l i2 in conjunction with a barometric jet |24, a diaphragm assembly |22 and an adjustable jet 24. The stem of the barometric jet carries a barometric bellows |25 of known type and function mounted in a chamber |28 connected to the air intake of the engine by a duct |30, so that the pressure around the bellows |26 is the total engine intake pressure. The flow area at the barometric jet |20 may be adjusted by a threaded adjusting screw |32 attached to the bellows sin |25. The barometric jet provides an altituderegulating valve for the flow of fuel from the chamber between the diaphragms H6 and |22, this fuel being passed through a duct |34 into the space in back of the diaphragm |22 and then through a control passageway |35 into a fuel return line |38 leading to the line 36. Any leakage around the needle of the barometric jet also flows into the line |3 from a duct |31. The diaphragm |22 carries a pin |38 for controlling passageway l 35 and is biased to the right by a spring 39.

The barometric belows |26 varies the area at the barometric jet |20 as a function of the total intake pressure. Any variations in the total intake pressure causes a corresponding change in position of the needle of the barometric jet and in the flow therethrough. This flow can be made any function of the total intake pressure desiredy by proiiling the barometric jet appropriately.

In equilibrium the forces on either side of the flexible diaphragm |22 must be equal. Thus the pressure on the spring side of the diaphragm is less than on the opposite side since the spring load plus the pressure load on one side must equal the pressure load on the other side. If the spring load plus pressure load is too low, pin |38 is moved toward closing till pressure increases. The opposite action is true if the opposite loading is true. The resulting pressure diiferential acting across diaphragm |22 which is maintained essentially constant by proper detail design acts in conjunction with the area of jet |20 to flow a quantity of fuel through jet |20 which is a function of total intake pressure. The total fuel flowing through the barometric jet |20 must come through the adjustable jet |24 which takes fuel at the pressure in the line 28 through a line |40, the fuel passing the jet |24 being delivered through a line |42 into the chamber between the diaphragms I I6 and |22. The only outlet to this chamber is through the barometric jet |20. Pressure drop across jet |24 may be adjusted by turning the threaded stem |44 when the apparatus is tested to give the desired ilow through the stand-by control, As a result of the relationships, described above, between the barometric jet |20 and its associated diaphragm assembly, the now through the adjustable jet |24 is a function of the total intake pressure of the engine.

The adjustable jet |24 and the speed jet |00 are supplied with fuel from the same intake line 28, therefore, the pressures in the inlet to these jets are equal. The pressure drop across the adjustable jet |24 creates a metering pressure across the speed jet |00 in the manner described below.

The diaphragm IIB may be referred to as a speed regulating diaphragm and it, in conjunction with the valve member |2, actuated thereby, maintain the outlet pressure at the adjustable jet |24 and the speed jet |00 equal to each other. An increase in pressure between diaphragms H6 and |22 tends to move the valve member i2 toward its seat until the outlet pressure at the speed jet is made substantially equal thereto. Therefore, the flow through the speed jet is determined by the area set by the plots lever which is a function of the selected speed, and by the metering pressure which is a function of the total intake pressure.

On one side of the diaphragm H6 the total force acting is equal to the pressure at the outlet of jet |24 times the diaphragm area. On the other side the total force equals the pressure existing at line 32 times the area of line 32 plus the pressure at the line lill timesthe remaining area at the diaphragm H6. The pressure at line 32 varies continually throughout an operating period and the resultant change in the pressure at line itl can adversely affect accuracy of metering into line 22 except for the action of spring H4. As pressure at line ,32 varies, valve H2 varies its position in order to create the appropriate pressure drop between line I'i and line 32. The varying position and Yload of and across valve H2 is matchedby the position and loading of spring ilfll so that the pressure at'line l'l is maintained essentially constant with the changes in pressures at line 32, thereby improving the accuracy of metering.

The apparatus of the present invention, including a combination of a stand-by control with a main control for a jet engine, provides a system which is automatic and eective:formetering fuel to the jet engine. The stand-by control of the improved system furthermore is Iarranged to effectively meter fuel tothe engine .advantageously at a rate slightly less than .that suppliedby .the main control. Themain control-maygovern the speed of the engine directly, whilethe stand-by control of the present apparatus associated therewith governs the speed vof the engine Yby scheduling fuel delivery accordingto engine speed and total intake pressure.

From the foregoing description-of the invention, it will be apparent that certain .changes may be made in various elements ofthe apparatus without departing from the vspirit and'scope of the invention, as dened by the appended claims.

What is claimed as new is:

l. In an apparatus .for controlling `the supply of fuel to jet engines including `a main control and a stand-by control, means including a pipeline for supplying fuel from a fuel supply and for delivering 'the fuel rto .the jet enginenozzle gallery, the fuelin said line being under control of the main control, a separate fuel supply line for supplying fuel from a fuel `supply to the stand-by control and connected .into 4the `line from the main automatic control leading tto rthe engine vnozzle gallery, a fuel .return .line connected into veach of said fuel supplyrlinea .valve means for controlling the flow of ifuelfromleach fuel supply line to the return line, a checkvalve in each of the fuel supplylines beyond saidnontrol valves, means for normally maintainingthe control valve between the .stand-by Y.fuel supply line and the yreturn Vline in open position,zineans for normally maintaining the valve :betweenthe main fuel supply line :and the return .line in closed position, and means responsive to a predetermined drop in pressure in the main Yfuel supply line between the maincontroland Ith'echeck valve in the line for closing the control valve between the stand-by `fuelsupply line andthe fuel return line.

2. .en apparatus for controlling .the supply :of fuel to jet engines asidened by claim l in .which each control valve includes a piston-like valve member, and a solenoid means :forcontrolling the movement o thepiston-lilremember.

3. An apparatus as definediby claim 2 in which each valve member is mounted inacylindrical chamber, a passageway for fuel from the Afuel supply line to the back portion yof .the-.chamber in which the piston-like member moves, .a passageway having an `orifice therein :leading from said chamber .to theireturnlinerand;asmall valve actuated-bythe solenoidmeans arrangedfto open and close the vpassageway from the fuel supply line.

4. An apparatus for-controlling the supply of fuel to jet engines asdened by claim l in which thecontrol valve between the stand-by fuel supply line and the fuel 4return line includes a piston-like valve member mounted for reciprocation in a chamber, a vpassager/yay leading from the stand-by fuel supply line to the chamber in back of the piston-like member, a passageway havin a leakage orifice leading from said chamber into the fuel return line, a small valve in the passageway leading from the stand-by fuel supply line, a solenoid for operating said small valve, and meansiassociated with the responsive means for controlling the energizing and the cle-energizing ofthe solenoid.

5. An apparatus for controlling the supply of fuel `to jet engines as defined by claim 1 in which the means responsive to a predetermined drop in pressure comprises an electric switch, an actuator means for operating said switch, and means for conducting fuel from the main fuel supply line between the main control and the check valve therein to said actuator means.

6. An apparatus as defined by claim 5 in which said actuator means includes a reciprocable piston-like shuttle member, means for biasing said shuttle member, and a valve in the passageway leading `to the shuttle member and responsive to the fuel pressure in the passageway.l

7. An apparatus for controlling the supply of fuel to jet engines as donned by claim l in which each control valve includes a relatively small solenoid-operated valve for controlling the actuation of a valve member for in turn controlling the flow of fuel to the return line, and means for energizing and deenergizing the solenoids of the solenoid valves.

8. An apparatus for controlling the supply of fuel to jet engines as defined by claim l in which the stand-by control is mounted in the stand-by fuel supply line between the control valve and the check valvetherein, the stand-by control including a speed jet through which fuel for the jet engine flows, and means for controlling the metering through said speed jet responsive to the total intake pressure of the engine.

9. An apparatus-as dened by claim 8 in which the speed jet includes pilot-controlled means for varying the area of the jet through which the fuel flows, a valve in the fuel supply line immediately following the speed jet, and means responsive to changes in pressure of the fuel after leaving the jet for controlling the valve in the line directly after the jet.

l0. An apparatus for metering fuel supplied to an engine, comprising a fuel supply line, a speed jet -in said line, Ameans for `manually controlling he iiow area'of said jet, a diaphragm control valve in the line downstneeun from the jet, the diaphragm being responsive to the pressure of the fuel flowing from the jet, a second diaphragm spaced from the diaphragm of the diaphragm valve and forming a chamber therebetween, means for-bypassing arestricted flow of fuel from the fuel supply'line'around the speed jet to said chamber, a passageway from said chamber to the space in back of the second diaphragm, and means responsive tothe total intake pressure oi' the engine for controlling the flow through said passageway.

l1. An apparatus as defined by claim 10 in which the valvezdown-.stream from the speed jet includes :a l'movable member Vmovable to open position by a biasing spring and toward a closed position by the diaphragm associated therewith, said second diaphragm being biased toward said chamber by a biasing spring, and means movable by said second diaphragm for varying the flow of fuel in said passageway.

12. An apparatus for controlling the supply of fuel to jet engines as claimed in claim 1, characterized in that the stand-by control is arranged in the stand-by fuel supply line between the control valve and the check valve therein and comprises a speed jet in the stand-by fuel supply line, means for manually controlling the flow area of said jet, a diaphragm control valve in the stand-by line down-stream from the jet, the diaphragm being responsive to the pressure of the fuel owing from the jet, a second diaphragm spaced from the diaphragm of the diaphragm Valve and forming a chamber therebetween, means for luy-passing a restricted flow of fuel from the stand-by fuel supply line around the speed jet to said chamber, a passageway from said chamber to the space in back of the second diaphragm, and means responsive to the total intake pressure of the engine for controlling the flow through said passageway.

13. In an apparatus for controlling the supply of fuel to jet engines including a main control and a stand-by control, means including a pipeline for supplying fuel from a fuel supply and for delivering the fuel to the jet engine nozzle gallery, the fuel in said line being under control of the main control, a separate fuel supply line for supplying fuel from a fuel supply tol the stand-by control and connected into the line from the main automatic control leading to the engine nozzle gallery, fuel return line means connected into each of said fuel supply lines, valve means for controlling the flow of fuel from each fuel supply line to the return line means, check valve means for each of the fuel supply lines beyond said control valves, means for normally maintaining the control Valve between the standby fuel supply line and the return line in open position, means for normally maintaining the valve between the main fuel supply line and the return line in closed position, and means responsive to a predetermined drop in pressure in the main fuel supply line between the main control and the check Valve means in the line for closing the control valve between the stand-by fuel supply line and the fuel return line.

14. An apparatus for controlling the supply of fuel to jet engines as defined by claim 13 in which the means responsive to a predetermined drop in pressure comprises an electric switch, an actuator means for operating said switch, and means for conducting fuel from the main fuel supply line between the main control and the check valve means therein to said actuator means.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,275,472 Samiran Mar. 10, 1942 2,302,014 Fausek Nov. 17, 1942 2,313,149 Jacobsen Mar. 9, 1943 2,330,558 Curtis Sept. 28, 1943 2,420,052 Muir May 6, 1947 2,435,982 Samiran Feb. 17, 1948 2,607,297 Walker et al Aug. 19, 1952 

